A voice over Long Term Evolution (VoLTE) capable mobile device is configured to deregister from an Internet Protocol (IP) Multimedia Subsystem (IMS) network element for voice connections and use a dual network mode of operation that includes data connections via a 4G LTE/LTE-A network and voice connections via a legacy 3G or 2G network based on performance metrics a serving cell of the 4G LTE/LTE-A network. When the performance metrics indicate that voice connections may be unstable, such as when a reference signal received power (RSRP) falls below a threshold level but remains above a reselection/handover threshold level, the mobile device deregisters from the IMS network element to disable VoLTE connections from being established. The mobile device establishes the requested voice connection via a legacy 3G or 2G network instead, while established or new data connections for the mobile device continue to use the 4G LTE/LTE-A network.
Legal claims defining the scope of protection. Each claim is shown in both the original legal language and a plain English translation.
1. A method to select a network mode for a mobile device, the method comprising: by the mobile device: in response to initiation of a voice connection, evaluating performance characteristics of a Lone Term Evolution (LTE) serving cell; when the LTE serving cell is suitable for the voice connection based on the evaluation, establishing the voice connection as a Voice over LTE (VoLTE) connection via the LTE serving cell; and when the LTE serving cell is not suitable for the voice connection: deregistering from an Internet Protocol Multimedia Subsystem (IMS) network element or ignoring a message from the LTE serving cell to establish the voice connection; and establishing the voice connection via a neighbor cell, wherein the mobile device maintains existing data connections and/or establishes new data connections via the LTE serving cell in parallel with the voice connection via the neighbor cell.
A mobile device selects a network for voice calls based on LTE cell quality. When starting a voice call, the device checks the LTE signal. If the LTE signal is strong enough for a good VoLTE call, the call is made over LTE. If the LTE signal is weak, the device disconnects from the VoLTE system (IMS) to prevent using VoLTE. Then, it makes the voice call using a 3G or 2G network (neighbor cell) instead, while keeping existing or starting new data connections over the LTE network simultaneously.
2. The method of claim 1 , wherein the LTE serving cell operates in accordance with an LTE radio access technology (RAT) and the neighbor cell operates in accordance with a legacy 3G or 2G RAT that is different from the LTE RAT of the LTE serving cell.
The method from the previous claim uses different radio technologies for voice and data. The mobile device uses 4G LTE for data and switches to a legacy 3G or 2G network for voice calls when the 4G LTE signal is not strong enough. This allows the device to maintain a data connection while making a voice call on an older network technology. The LTE network and the 3G/2G network operate using different radio access technologies (RATs).
3. The method of claim 1 , wherein the performance characteristics of the LTE serving cell comprise a reference signal receive power (RSRP), and suitability of the LTE serving cell for the voice connection is based at least in part on comparing the RSRP of the LTE serving cell to a threshold.
The method from the first claim determines the suitability of the LTE network for voice calls by measuring the reference signal received power (RSRP) of the LTE cell. If the RSRP is above a specific threshold, the LTE network is considered suitable for VoLTE calls. Otherwise, the call is made over a 3G or 2G network. This ensures that VoLTE calls are only established when the LTE signal strength is adequate.
4. The method of claim 3 , wherein the threshold exceeds a threshold specified by the LTE serving cell for reselection or handover.
The RSRP threshold used to determine if the LTE network is suitable for voice calls, as described in the previous claim, is set higher than the thresholds used for cell reselection or handover on the LTE network. This means that the device only switches to 3G/2G for voice when the LTE signal is significantly weaker than what would normally trigger a cell change, ensuring VoLTE is used whenever reasonably possible.
5. The method of claim 1 , wherein the neighbor cell operates in accordance with a code division multiple access (CDMA) 1× radio access technology (RAT).
The neighbor cell used for voice calls when the LTE signal is weak, as described in the first claim, operates using CDMA 1x radio technology. This means that the device uses a CDMA 1x network as the fallback option for voice calls when VoLTE is not suitable due to poor LTE signal strength.
6. The method of claim 1 , wherein the initiation of the voice connection comprises a user input to the mobile device to establish the voice connection.
The initiation of the voice call, which triggers the network selection process in the first claim, is started by a user action on the mobile device. For example, the user might press a button on the phone to dial a number. This user action triggers the mobile device to evaluate the LTE signal and decide which network to use for the voice call.
7. The method of claim 1 , further comprising: by the mobile device: when the LTE serving cell is not suitable for the voice connection and the initiation of the voice connection comprises receipt of the message from the LTE serving cell to establish the voice connection: listening for a paging request from the neighbor cell, and the establishing the voice connection via the neighbor cell occurs in response to receipt of the paging request from the neighbor cell.
If a voice call is initiated by a message from the LTE network (instead of the user), and the LTE signal is weak, as described in the first claim, the device listens for a page from the 3G/2G network. The voice call is then established using the 3G/2G network in response to receiving this paging request. The mobile device ignores the message from the LTE network requesting the voice call to be established on LTE.
8. The method of claim 1 , wherein the neighbor cell operates in accordance with a code division multiple access (CDMA) 1× radio access technology (RAT).
The neighbor cell, used for voice calls when the LTE signal is weak as described in the first claim, uses a CDMA 1x radio access technology (RAT). This acts as the fallback network for voice when LTE is not adequate.
9. The method of claim 1 , wherein: the performance characteristics comprise two or more of: a signal power, a signal quality, an error rate, or a measure of loading of the LTE serving cell, and the LTE serving cell is not suitable for the voice connection when at least two of the performance characteristics do not satisfy corresponding thresholds.
The first claim uses multiple factors to determine LTE suitability for voice. These factors include signal power, signal quality, error rate, and LTE cell load. The LTE network is considered unsuitable for voice calls only when at least two of these measurements are below their respective thresholds. This provides a more reliable determination of network suitability than using a single measurement.
10. A wireless communication device comprising: wireless circuitry; one or more processors communicatively coupled to the wireless circuitry; and a memory communicatively coupled to the one or more processors, wherein the one or more processors are configured to execute computer-executable instructions stored within the memory to cause the wireless communication device to: measure a reference signal received power (RSRP) of a serving cell and one or more neighbor cells; in response to detecting a voice call initiation, compare the measured RSRP of the serving cell to a radio access technology (RAT) specific threshold, wherein the RAT specific threshold exceeds a threshold for reselection or handover specified by the serving cell; when the RSRP of the serving cell equals or exceeds the RAT specific threshold, establish a voice connection via the serving cell; and when the RSRP of the serving cell falls below the RAT specific threshold and a neighbor cell of the one or more neighbor cells satisfies a threshold for establishing the voice connection, establishing the voice connection via the neighbor cell, wherein: the wireless communication device maintains existing data connections and/or establishes new data connections via the serving cell in parallel with the voice connection via the neighbor cell, and when the voice call initiation comprises a mobile-originated voice call, the wireless communication device deregisters from an Internet Protocol Multimedia Subsystem (IMS) network element before establishing the voice connection via the neighbor cell.
A mobile device selects network based on LTE signal strength. The device measures LTE and neighbor cell signal strength (RSRP). When a voice call starts, the LTE RSRP is compared to a specific threshold. This threshold is higher than thresholds for normal cell switching. If LTE RSRP is high enough, use LTE for voice. If LTE RSRP is too low, and a neighbor cell has adequate signal, use the neighbor cell for voice. While using the neighbor cell for voice, the mobile device keeps or makes new data connections on LTE. For outgoing calls when LTE RSRP is too low, the device disconnects from the VoLTE system before using the neighbor cell for voice.
11. The wireless communication device of claim 10 , wherein the wireless communication device is a multi-mode communication device that is capable of voice over LTE (VoLTE) communications with the serving cell and circuit-switched voice communications with the neighbor cell.
The wireless communication device described in the previous claim is a multi-mode device. It is capable of making VoLTE calls over the LTE network and circuit-switched voice calls over the 3G/2G network. This allows it to seamlessly switch between the two technologies depending on the LTE signal strength.
12. The wireless communication device of claim 10 , wherein: when the voice call initiation comprises a message from the serving cell indicating a request to establish the voice connection, the wireless communication device: ignores the message from the serving cell, listens for a paging request from the neighbor cell, and establishes the voice connection via the neighbor cell in response to receipt of the paging request from the neighbor cell.
In the scenario from claim 10, when the network initiates a voice call and the LTE signal is poor, the device ignores the network's request to use LTE for voice. Instead, the device listens for a page from the neighbor cell. If a page is received, the device uses the neighbor cell for the voice connection, as described in the previous claim.
13. The wireless communication device of claim 10 , wherein the serving cell operates in accordance with a Lone Term Evolution (LTE) wireless communication protocol, and the neighbor cell operates in accordance with a code division multiple access (CDMA) 1× wireless communication protocol.
The serving cell in the wireless communication device of claim 10 operates using the LTE wireless communication protocol. The neighbor cell, which is used for voice calls when the LTE signal is poor, operates using the CDMA 1x wireless communication protocol.
14. A non-transitory computer-readable medium that stores instructions that, when executed by one or more processors, cause a wireless communication device to: in response to initiation of a voice connection: evaluate performance characteristics of a Lone Term Evolution (LTE) serving cell; when the LTE serving cell is suitable for the voice connection based on the evaluation, establishing the voice connection as a Voice over LTE (VoLTE) connection via the LTE serving cell; and when the LTE serving cell is not suitable for the voice connection: deregistering from an Internet Protocol Multimedia Subsystem (IMS) network element, and establishing the voice connection via a legacy 3G or 2G neighbor cell, wherein the wireless communication device maintains existing data connections and/or establishes new data connections via the LTE serving cell in parallel with the voice connection via the legacy 3G or 2G neighbor cell.
A non-transitory computer-readable medium with instructions to switch between LTE and 3G/2G for voice calls. The instructions, when executed, cause the mobile device to check LTE signal quality when a voice call is started. If the LTE signal is good enough, the call uses VoLTE. If the LTE signal is weak, the device disconnects from the VoLTE system (IMS) and uses a legacy 3G/2G network for the voice call, while keeping or creating data connections over LTE.
15. The non-transitory computer-readable medium of claim 14 , wherein the LTE serving cell is suitable for the voice connection when one or more performance characteristics of the LTE serving cell satisfy corresponding thresholds, wherein at least one threshold comprises an LTE-specific threshold that exceeds a threshold for reselection or handover specified by the LTE serving cell.
As in claim 14, LTE suitability is determined by comparing signal quality measurements to thresholds. At least one of these LTE thresholds is set higher than the thresholds used for cell reselection or handover. This ensures that VoLTE is preferred unless the LTE signal is significantly degraded.
16. The non-transitory computer-readable medium of claim 14 , wherein the legacy 3G or 2G neighbor cell operates in accordance with a code division multiple access (CDMA) 1× radio access technology (RAT).
The 3G/2G network used as a fallback option for voice calls in claim 14 operates using the CDMA 1x radio access technology.
17. The non-transitory computer-readable medium of claim 14 , wherein the initiation of the voice connection comprises detecting a request to establish a mobile-originated voice call.
The voice call initiation in claim 14 is triggered by a request to make an outgoing call from the mobile device.
18. The non-transitory computer-readable medium of claim 14 , wherein execution of the instructions further causes the wireless communication device to: periodically evaluate the performance characteristics of the LTE serving cell; and re-register with the IMS network element, when both the performance characteristics of the LTE serving cell indicate that the LTE serving cell is suitable for voice connections and the wireless communication device is not registered with the IMS network element.
The computer-readable medium from claim 14 includes instructions for periodically checking the LTE signal strength. If the LTE signal is good enough for voice calls and the device is not currently registered with the VoLTE system (IMS), the device will re-register with the IMS. This allows the device to switch back to VoLTE when the LTE signal improves.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
May 29, 2015
July 11, 2017
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